Researchers are still a long way from finding the fountain of youth, but new studies suggest that two long-used medications might have anti-aging benefits.

For decades, scientists have tackled diseases of aging, like cancer and heart disease, but in recent years some have begun to express confidence that they will find a treatment for aging itself.

In a study released Wednesday in Science Translational Medicine, a medication similar to the transplant drug rapamycin was shown to boost the immune system of older people getting a flu vaccine. Vaccines generally becomes less effective in people over 65 because their immune systems don't respond well; taking a rapamycin-like drug for six weeks improved the flu vaccine's effectiveness by 20%, according to the study.

The trial was the first to look at whether the age-defying benefits of the drug seen in other animals might work in people, said Joan Mannick, executive director of the New Indications Unit of the Novartis Institutes for BioMedical Research, a division of the pharmaceutical giant Novartis.

A second study found that ibuprofen comparable to what people use extended the lifespan of yeast, worms and flies.

It's too early to know whether the drug will have the same effect in people, how long it would need to be taken or at what doses, researchers said. But "it's exciting because we know (ibuprofen) can be used relatively safely in humans," said Matt Kaeberlein, an expert in the biology of aging at the University of Washington, who worked on the study.

Other drugs such as aspirin and the diabetes drug metformin have also shown some broad-spectrum effects against aging, said Brian Kennedy, president and CEO of the Buck Institute for Research on Aging in Novato, Calif., which worked on the ibuprofen study.

"It may be that we don't have to wait for a magic new drug," Kennedy said, but that drugs we already know and use could extend healthy lifespan.

The ibuprofen study, which was published in the journal PLOS Genetics, found that the drug inhibits the cell's use of tryptophan — an amino acid made famous for its role in post-Thanksgiving sleepiness. Less tryptophan in the animals led to longer lives. Previous studies have suggested that people who took ibuprofen long-term had a lower risk of developing Parkinson's or Alzheimer's disease.

With rapamycin, there's an "accumulating mountain of information" suggesting that it extends lifespan in mice, Kaeberlein said, and the new study is the "first indication that some of these effects and maybe all of them are conserved (in people)."

All the researchers urged caution about the idea of popping a daily pill to push off death. It's still unclear whether extending healthy life is possible. But these studies and others are increasingly suggesting that it is, Kaeberlein said.

Even if a drug is shown to extend human life, it's too soon to tell what the trade-off for that life extension might be. Severely restricting calories, for instance, which has been shown to extend life in mice and other animals, also limits fertility and seems to compromise the animals' immune systems.

Kaeberlein said people shouldn't yet be taking any of these drugs in hopes of life extension. But he does plan to start giving rapamycin to his dog soon, as part of a clinical trial to see if it helps reduce heart disease and allows pets to live longer, healthier lives.